Method and apparatus for differential quenching of heat treated metallic articles



28903 75 QUENCHING 4 Sheets-Sheet 1 INVENTOR. ML 715/? hhfiom LEA/z H.LENZ OF HEAT TREATED METALLIC ARTICLES June 16, 1959 METHOD ANDAPPARATUS FOR DIFFERENTIAL Filed April 26, 1955 E AA/M EWA June 16, 1959w. H. LENZ 2,890,975 METHOD AND APPARATUS FOR DIFFERENTIAL QUENCHING OFHEAT TREATED METALLIC ARTICLES Filed April 26, 1955 4 Sheets-Sheet 2 W/Mf A k IN VENTOR.

M1727? 6612010 [EA/Z MI? 55 w Arrows June 16, 1959 w. H. LENZ 2,390,975

METHOD AND APPARATUS FOR DIFFERENTIAL QUENCHING OF HEAT TREATED METALLICARTICLES 4 Sheets-Sheet 3 Filed April 26, 1955 w mn A TTORNEKS June 16,1959 w H LENZ 2,899,975

METHOD AND APPARATU FDR DIFFERENTIAL QUENCHING OF HEAT TREATED METALLICARTICLES Filed April 26, 1955 4 Sheets-Sheet 4 INVENTOR. ML 727? 544F010151/2 WA TOHNEYS United States Patent Walter Harold Lenz, Washington,111., assignor to C ater- ?illar Tractor Co., Peoria, 111., acorporation of Caliornia Application April 26, 1955, Serial No. 503,935

11 Claims. (Cl. 148-2156) This invention relates to zone controlledquenching of heated metallic articles, and more particularly to theprovision of a desired hardness pattern in a metallic article byquenching the article with a sheet of quench fluid that has coexistingzones of fluid with different heat abstraction properties.

When a metallic article having a non-circular cross section is heatedand then hardened by subjecting it to uniform quenching, the articlebecomes distorted and it may even develop cracks. A particularlydifficult problem is encountered with a severe quench, such as a waterquench, which rapidly extracts heat from the metallic articlef As aresult, severe quenches have not been employed to any appreciable extentin the quenching of articles that do not have circular cross sections,although such quenches produce a very hard metallurgical structure.

The distortion produced. upon uniformly quenching a metallic articlehaving a non-circular cross section is caused by the difference in thecooling rate of surface portions that are adjacent sections of thearticle of varying size. When the mass or cross sectional area of ametallic article adjacent a perimeter portion of the cross section iscomparatively large, a relatively large amount of heat will be containedin the article adjacent such perimeter portion. Since a uniform quenchextracts heat at the same rate from all parts of the article, thesurface portions of the article adjacent the thick sections will coolless rapidly than the surface portions adjacent the thin sections whichcontain the smallest quantity of heat.

Formation of a hard layer of martensite requires rapid cooling of thesteel article. Consequently, a thin layer of hard martensite is formedon the thick areas of a metallic article that cools slowly, whereas thethin areas that are rapidly cooled to a greater depth have a relativelythick layer of martensite formed by the quench. The difference in thecooling rate of various parts of the article, and the resultantunevenlayer of the hard martensite, which is of lower density than theremainder of the article, produce stresses which result in cracking anddistortion. Articles that are of considerable irregularity cause thegreatest problem, and the use of a uniform water quench with sucharticles has been unsatisfactory. As a result, irregularly shaped,elongated articles such as track shoes for tractors are usually made ofhigh carbon steel, and they are quenched by placing the articles in amild, oil bath quench. However, the hardness layer obtained in an oilbath quench is of uneven thickness, and the resultant stresses areundesirable.

To summarize this invention, it comprises controlling the hardnesspattern in a heated metallic article by subjecting the article to asheet of quench fluid that has coexisting zones of fluid with regulatedheat abstraction properties. In this manner the rate of cooling of allportions of a non-circular metallic article can be controlled byabstracting heat more rapidly from thick areas that contain the greatestamount of heat. Best results in reducing distortion resulting fromquenching of noncircular articles is obtained in accordance with thisinvention by subjecting the entire perimeter of a cross section of thearticle to a scanning sheet of quench fluid, and elfecting relativemovement between the article and the quench fluid. The perimeter area ofthe article is then uniformly hardened progressively as the sheet ofquench fluid passes over the surface of the article. However, ifdesired, the zone controlled sheet of quench fluid may also be employedto produce deliberate distortion or to produce any desired hardnesspattern in an article of either circular or non-circular cross section.

The apparatus of this invention for directing a sheet of zone controlledquench fluid onto a heated metallic article has a manifold with anopening of sufiicient size to receive the article, orifice meanscommunicating with the manifold for directing a substantially continuoussheet of quench fluid to said article, and zone control of the heatabstraction properties in the sheet of fluid. The orifice may be eitheran elongated opening or a series of closely spaced smaller openingswhich produce the effect of an elongated orifice as long as the sheet issubstantially continuous or without cavitation as it strikes the heatedmetallic article. Control of the heat abstraction propcities in zones offluid in the sheet is accomplished by varying the volume or temperatureof liquid flowing into a zone, or by varying the orifice size in. zonesto provide for a different volume of fluid in such zones, or by acombination of such means.

By employing a sheet of quench fluid with the heat abstractingproperties controlled in zones, a non-circular or irregular article maybe quenched with a severe quench, such as water, to produce a hardsurfaced, distortion free article having a substantially uniformhardness pattern. The resultant new article has not been produced by anyother method. As previously explained, uniform quenches cause distortionor cracking. Also, quenches directed to portions of an article fromdifferent sizes of relatively large, separated nozzles are notcontinuous or cavitation free unless arranged in accordance with thisinvention to provide a substantially continuous sheet. Furthermore, aquench that is progressively variable, with the volume either graduallyincreasing or decreasing along the length of a sheet of quench, can notproduce the results of this invention in which separate zones arecontrolled independently of adjacent zones in the sheet.

For purposes of illustration, the present invention is disclosed in itsapplication to the quenching cycle in the heat-treatment of track shoesof the type commonly employed on track-type tractors, though it will beunderstood from the following description that the invention is notlimited to this particular type of article but is readily adaptable toother fields Where it is desirable to control the hardness pattern in anarticle.

In the drawings:

Fig. 1 is an isometric view, with parts broken away, schematicallyillustrating a progression of track shoes in end-to-end abutmentpropelled by a power conveyor through quenching apparatus embodying thepresent invention;

Fig. 2 is a vertical transverse section taken through the apparatusparallel to the quench block illustrating the relation of the quenchmanifold to the shoes;

Fig. 3 is a vertical section through the quench manifold takensubstantially along the line III-III of Fig. 2;

Fig. 4 is a view in front elevation of the quench manifold with partsbroken away to show the details thereof;

Fig. 5 is an enlarged fragmentary view of the quench manifold inelevation illustrating a modification of the nozzle formation thereoffor supplying an increased volume of quench to critical zones of thetrack shoe;

Fig. 6 is a fragmentary section of the modified nozzle takensubstantially along the line VI-VI of Fig.

Fig. 7 is a schematic view illustrating a further rnodification of theinvention in which the heat abstraction properties of the quench arecontrolled by regulating the fluid temperature;

Fig. 8 is a vertical section taken through a track shoe illustratingquench pressures and orifice openings employed for quenching such anarticle. The numbers closest to the track shoe indicate the size of theorifice opening in inches, and the outer numbers specify gauge pressuresof the quenching fluid in pounds per square inch; and

Fig. 9 is a vertical section taken through a quenched track shoe withphantom lines indicating the depth of the hardness layer. The degree ofhardness in the Rockwell C scale of various parts of the track shoeappears on the drawing, and reference characters as well as crosshatching have been omitted for clarity.

Fig. 1 discloses the quench apparatus 10 positioned adjacent thedischarge opening of a heating element 11, shown herein for the purposeof illustration as an electric furnace. Since the furnace forms no partof this invention, it is to be understood that any of the well-knowntypes of heating elements, such as induction coils, or a gas furnacewill function equally as well. A power conveyor 12, driven by a suitabledriving arrangement, herein disclosed as a variable speed motor 13,feeds a continuous line of track shoes through the quench apparatus 10at a preselected rate. The track shoes are preferably fed into thequench apparatus in end-to-end abutment to provide a relativelycontinuous surface of material passing therethrough.

A quench manifold interposed between spaced rollers 21 of the powerconveyor 12 is provided with a suitable opening 22 to permit passage oftrack shoes therethrough. Quench water is supplied to the manifold 20through a conduit 23 provided with a thermostatically controlled mixingvalve 24 so that quench fluid returned to the manifold 20 through aconduit 26 from an accumulator tank, not shown, may be mixed with asupply of cold water entering said manifold 20 through a line 27, withvalve 24 maintaining the quench fluid at a desired temperature.

Quench fluid is directed to the entire perimeter surface of the trackshoe as it passes through the quench block. A flexible wiping member 28secured to a plate 29 is adjustably retained in spaced relation to thequench manifold 20 to remove accumulations of quench fluid which clingto the top surface of the track shoe. This terminates the extraction ofheat by the quench fluid within a given longitudinal distance from thequench block, thereby preventing undesirable continued cooling of thetrack shoe. However, satisfactory results may be obtained without use ofwiping member 28 and it is not essential.

In Fig. 2, the manifold 20 is disclosed as comprising a supply tank 31and a quench block 32 integrated therewith. Heated track shoes 15 aredirected therethrough by way of opening 22 as previously described. Theshape of the opening 22 is preferably varied to conform to theparticular shape of any article to be treated but as herein disclosed,conforms to the general configuration of a single grouser track shoe.

Referring to Figs. 3 and 4, spaced quench directing chambers 33, areformed in quench block 32 and are arranged to generally parallel theshape of the opening 22. As best disclosed in Fig. 3, flow directors 36integral with cover plates 37 are retained in said chambers 33 in.spaced relation therewith to provide a curved flow path terminating in areduced elongated orifice or nozzle 38 formed by the edges 41 and 42 ofthe cover plates 37 and the bottom of chambers 33, respectively, whichwill direct a scanning sheet of water at an angle to the entire surfaceof the track shoe progressively .as it moves at a controlled ratetherethrough. A plurality of small orifices may be substituted forelongated orifice 38 providing they are small and closely spaced toproduce a substantially cavitation free sheet of quench fluid. Thismodification is readily accomplished by extending the cover plates 37over orifices 38 and drilling a plurality of small openings. Variationsin the size and number of such small orifices may be used to provide anadditional zone control over the quench. However, best results areobtained with an elongated orifice which produces a more uniform sheetof quench fluid.

Generally speaking, the plate portion 45 of the track shoe 15 must besubstantially flat, and free of distortions to avoid overstressing theshoe during operation. Due to the differences in the rate of heatabstraction of the disproportionate surface and volume variablesinherent in an article such as a track shoe, and due also to the unequalrate of volume change resulting from metallurgical transformation duringquenching, it has been economically impractical to prevent stresscracking or damaging distortion in certain zones of the plate.

In the present invention, in order to counteract these stresses, quenchblock 32 is provided with additional spaced chambers 46 and 47 which aredivided into subchambers or zones 48 by suitable partitions 49 whichextend into directing chambers 33 up to a short distance from orifice 38for best separation of the zones. In this manner directing chambers 33are divided into subchambers 50. Each sub-chamber or zone 48 isconnected to supply tank 31 as by independent conduits 51. Suitablecontrol valves 52 and pressure gauges 53 are associated with eachconduit 51 to permit control of the pressure and volume of quench watersupplied to each sub-chamber or zone 48.

Cover plates 37 are secured to block 32 as by capscrews 54. The greaterportions of the faces of walls 57 of merging chambers 33 are spaced fromcover plate 37 to provide channels 58 as indicated in Figs. 3 and 6 forcommunication of chambers 46 and 47 with directing chambers 33.

In operation, a continuous supply of quench water is pumped, by meansnot shown, into supply tank 31 to maintain it constantly under a desiredpressure, while the thermostatically controlled mixing valve 24maintains the quench at a desired temperature. Quench flows into theseveral zoned chambers 48 at a controlled volume and pressure in eachzone as explained. From chambers 48 the fluid passes through thechannels 58 and enters the subchambers 50 of directing chambers 33, withthe fluid in each chamber having its particular controlledcharacteristics. The flow director 36 positioned in each cham ber 33provides a curved path for the flow of water so that it is expelled fromthe quench block through elongated orifice 38 as an uninterrupted sheetwith a minimum of turbulence and with zones of varying pressure andvolume throughout its length. The separate zones of fluid automaticallymerge at their edges so that the change of quench characteristicsbetween zones is not abrupt.

The orifice 38 may be adjusted to vary the volume and pressure of quenchfluid by providing slightly elongated or enlarged holes 61 in coverplates 37 so as to permit movement of the plate before the cap screws 54are tightened.

When conditions require, it may be necessary to further alter thecharacter of quench in areas or zones where the area of the crosssection is very large compared tothe surface area, as for instance, inthe portion of the track Shoe opposite the grouser. In order that therate of heat abstraction may be increased in such zones the portion ofthe nozzle opening directing quench water to these areas may be enlargedas indicated at 62 (see Figs. 5 and 6) to provide an increased flow ofquench. If desired, the quench volume may be entirely controlled by mPying an orifice .of carefully adjusted size in different zones withoutthe use of the partitioned sub-chambers 48 and 50, and independentconduits 51. However, such an apparatus does not have the advantage ofthe flexible controls shown in the drawing. Variable controls for theheat abstracting properties of zones of quench are important for makingadjustments for temperature variations in the steel and for differentcharacteristics of various mill heats of steel.

As described to this point the effect of quench on different zones ofthe perimeter of an advancing article is controlled by deliveringdifferent volumes of quench to the separate zones. A similar effect maybe obtained by varying the temperature of quench liquid delivered to thezones. Means for varying the temperature of the quench in differentzones is schematically illustrated in Fig. 7. In this figure, aplurality of thermostatically controlled mixing valves 24a areinterposed between conduits 26a and 27a to supply quench at selectedtemperatures through conduits 23a to each of a plurality of supplycompartments 31a formed in the supply tank 31 by partitions 31b. Eachcompartment 31a registers with one of the sub-chambers 48 through itsrespective conduitSl; thereby providing a continuous sheet of quenchwith zones of different delivery temperatures. It is also possible tocombine the two methods described so that temperatures and volume ofquench liquid may both be controlled in zones to obtain a desiredhardness pattern.

Thus, substantially distortion free parts are produced by employing asheet of zone controlled quench that impinges the entire perimeter of across-section of the article and passes progressively over the entirearticle.

In some instances. it is desirable to more accurately define therearward limit of the quench area and prevent quench fluid fromsplashing rearwardly outside the quench area. To this end quench block32 is provided with an air manifold 63 (Fig. 3) having an inlet 64 and aplurality of aligned orifices 66 which are positioned adjacent to theelongated nozzle 38. A supply of air under pressure is directed throughorifices 66 to maintain a wall of air adjacent the sheet of water toconfine the quench within the area desired.

Due to the fact that the quench clings to the upper, relatively flatsurface of the shoe and rapidly falls from the lower surfaces thereofbecause of gravity, a critical unbalance of internal stresses may exist,and cause distortion. To counteract these stresses, the quench block maybe adjusted vertically relative to the plane of moving track shoes bythe provision of suitable horizontal slots 67 (Fig. 2), formed inbrackets 68 integrated with the quench block 32 and a verticallydisposed slot 69 in one of the brackets 71 secured to the side plates 72of quench apparatus 10.

By increasing the distance between the upper surface of the article andthe quench nozzle, and decreasing the distance between the article andthe nozzle along the lower surface, said lower surface of the article isimpinged by the sheet of quench before its upper counterpart. In thismanner the effect of quench falling more rapidly from the lower surfacedue to the efiect of gravity may be counteracted.

A plurality of manifolds 76 (Figs. 1 and 3) each containing at least oneorifice 77, are positioned within the quenching apparatus prior to thequench block 20. As the track shoes are conveyed from the furnace 11toward the quench block, jets of air or other coolant may be directed tocritical areas, such as bolt holes and notches, normally present inarticles of this character.

Air under pressure or other suitable quench fluid is directed to eachmanifold 76 through conduits 78 leading from a pressurized supply header79. Individual control valves 81 in each conduit 78 permit selectivecontrol of pressure to its respective manifold. Thus, stress cracksusually caused by water quenching critical edges surrounding boltholesand notchm in, an article of this type may be avoided by pre-coolingthese areas below the critical temperature, prior to quenching.

If desired, the apparatus of this invention may also be employed toproduce a uniform scanning quench without use of the zone controlfeatures. The flow directors 36 and elongated orifice 38 produce a sheetof quench that impinges the heated metallic article at an angle, and thesheet encircles substantially the entire article. Such an apparatus forprogressively quenching an entire article with a uniform quench isuseful in many applications in which the cross section of the article isnot of great irregularity, or when it is desired to deliberately producedistortion upon quenching.

Although any shape of metallic article can be quenched in accordancewith this invention, the greatest usefulness is obtained in thequenching of elongated irregular articles. Such articles becomedistorted by uniform quenching, as previously explained, and the,problem has been particularly vexing. Even a regularly shapednon-circular article, such as an article with a square cross section,has less heat adjacent the corners than is contained adjacent otherportions of the perimeter of its cross section. Thus, uniform quenchingof such a square article produces the greatest depth of hard martensitein the corners of the article. This can be remedied by the zonecontrolled quenching hereof in which a zone of fluid having lower heatabstraction properties is directed at the corners. However, if desired,the zone controlled. sheet of quench fluid may also be employed toproduce deliberate distortion or to produce any desired hardness patternin an article of either circular or non-circular cross section.

The apparatus disclosed is particularly adapted to quench articles thathave congruent parallel cross sections. As the article moves past thequench block in a direction normal to parallel, substantially congruentcross sections, the peri-meters of successive cross sections then aresubjected to the same effective quenching. If the article is quenchedsuccessively along similar cross sections that increase or decrease insize, the depth of the hardness pattern will accordingly decrease ,orincrease unless a timed proportional control for the entire sheet ofquench fluid is employed.

Any heat treatable steel article may be quenched to provide a desiredhardness pattern by the method hereof. Steel articles, particularlythose of irregular cross section, that become distorted and cracked whenwater quenched by other methods, may readily be quenched withoutdistortion or cracking by the method of this invention. If both thecarbon content and alloy content of the steel are so high that waterquenching renders the hardness layer undesirably brittle and deep, azone controlled oil quench may readily be employed in accordance withthis invention. As is well known in the art, oil is a milder quench anddoes not produce the degree of hardness that is obtained with a waterquench. Also, it is commonly known that when identical steel articles ofthe same thickness and temperature are quenched with the same type ofquench, the degree of hardness is primarily dependent upon the carboncontent of the steel, and the depth of hardness depends upon the amountof other alloying compounds, such as manganese. Thus, the type of quenchmay readily be adapted to the particular steel that is to be employed.

Articles quenched by the zone controlled scanning sheet of thisinvention are preferably heated uniformly throughout to above thetemperature of transformation of the article prior to the quenching. Theresultant quenched article hasa tough, ductile center composed ofproducts of transformation, such as martensite, ferrite and pearlite,and an outer hard shell of martensite. If only the surface of thearticle is heated to above the temperature of transformation for thesteel in order to form austenite, which exists only above thetemperature of transformation, then the interior of the article will not7: be as tough and flexible after quenching as when the article isheated uniformly throughout.

After the article has been heated, it is quenched with the describedsheet of quench fluid that has zones of controlled heat abstractionproperties. It is well known that cold fluid has greater heatabstraction properties than warm fluid. Also, the greater the quantityof the liquid quench, the larger the amount of heat that is abstracted.As previously described, the quantity of quench is readily regulated bycontrolling either the pressure, or the size of the orifice, or both.The nature of the quench also determines its heat abstractionproperties. For example, a water quench extracts heat much more rapidlythan an oil quench. Consequently, the foregoing factors are controlledin zones to provide different desired heat abstraction properties insuch zones.

A sheet of quench that is free of cavitation, or in other words,substantially continuous along its length of contact with the article,is desirable for avoiding stress producing voids in the quench sheet andin the resultant hardness pattern. One sheet substantially continuousalong the upper half of an article, and another sheet substantiallycontinuous along the lower half are generally employed. Also, in orderto avoid distort-ion, a sheet of quench fluid is preferably employedthat surrounds the article and quenches progressively the perimeters ofparallel cross sections of the article. The use of a relatively thinscanning quench that progressively quenches the entire surface of thearticle, in combination with zone control of the heat abstractionproperties in the quench sheet, enables quenching of very irregulararticles without substantial distortion, even when a water quench isemployed.

The zone controlled quench of this invention is employed to preventdistortion upon quenching articles of irregular cross section byproviding a zone of quench fluid with the greatest heat abstractionproperites for quenching the thickest portions of the article, sincethese portions contain the greatest quantity of heat. Zones of quenchfluid of proportionally less heat abstraction properties are employedfor the portions of the article that have smaller masses per unit ofsurface area, and which as a result contain less heat.

The final adjustments for providing a suitable balance of heatabstraction properties in the various zones of quench fluid are readilymade by observing the distortion produced in the article upon quenching.The proportional heat abstraction properties of zones of fluidcontacting portions of the article in which concave distortion wasinitially produced is increased to remedy such distortion, and theproportional heat abstracting properties are decreased in areas thathave convex distortion. The distortion may be observed by comparin thequenched article with the original unquenched article, or by merelyplacing a straight edge along linear portions of the article. The. hardmartensite layer produced by the quench is less dense than the remainderof the article. Therefore, when the martensite layer is not of uniformthickness, the resultant distortion is apparent and it may be correctedby accordingly adjusting the heat abstraction properties in the zones ofquench fluid. In this manner, a substantially uniform hardness patternmay readily be produced in the article by adjusting the zones of quenchfluid until the quench cools all surface portions of the article atapproximately the same rate and to the same depth. Upon cutting a crosssection through the quenched metal, the depth of the hardness layer isvisually apparent because its color is lighter than the interior of themetal article.

When an irregularly shaped article is heated throughout and quenched bythe method of this invention, 'a substantially uniform depth and degreeof hardness is obtained in the article, and a tough inner core is formedthat contains products of transformation, such as pearlite, ferrite, andmartensite. The hardness layer is composed primarily of martensite, andthe degree of hardness grad ually decreases towards the inner edge ofthe layer. As illustrated in Fig. 9, there is an abrupt decrease inhardness at the inner boundary of the hardness layer, and the inner coreof the article is relatively soft and ductile. The chemical compositonof the article hereof remains the same throughout, although themetallurgical state is changed by the quenching.

If an irregular article is quenched by a uniform quench, such as byplunging it into a quench bath, an uneven hardness pattern is produced.Furthermore, although the well known carburizing method of hardening,which is expensive and time consuming, produces a uniform hardnesspattern, the resultant carburized article is different from the articleof this invention in other respects, such as in the decrease of carboncontent towards the interior of the article. Consequently, the irregularelongated article of this invention having a series of congruentparallel cross sections along a substantial portion of its length, auniform chemical composition, and which has been quenched to produce asubstantially uniform hardness pattern, is a new and distinct article.

After the article has been quenched, it may be tempered as desired. Theselective tempering disclosed in United States Patent No. 2,549,930 isparticularly useful for use in tempering articles produced in accordancewith this invention.

The following is a specific example of the use of the zone controlledquench of this invention as applied to the quenching of a track shoe fora track-type tractor.

A track shoe having a configuration of the shoe in Figs. 8 and 9 arequenched by the zone controlled scanning quench hereof. The track shoewas made from steel of S.A.E. specification #1039. In addition to iron,the steel contained the following percent by weight of other compounds:Carbon 0.36%, manganese 0.80%; sulfur 0.19%; phosphorus 0.031%; silicon0.21%; nickel 0.05%; chromium 0.05%; molybdenum 0.02%, and copper 0.05%.The length of the track shoe is 24 inches, the width is 9 inches, thethickness of the plate portion inch, and the height of the grouser tipabove the plate portion is 2 inches. A one foot length of the track shoeweighs 25.21 pounds.

The track shoe was heated throughout to a temperature of approximately1550" F. in a furnace. As the track shoe was conveyed to the quenchblock on apparatus of the type illustrated in Fig. 1, the temperaturedropped and it was about 1500 F. at the time of quenching. The rate ofmovement of the track shoe was 2.27 feet per minute.

The track shoe was then subjected to a water quench of a uniformtemperature of about F. The size and location of the orifice openingsare given in Fig. 8. Also, the pressure employed in pounds per squareinch gauge pressure, and the zones of such pressures are specitied inFig. 8. The total volume of quench employed was gallons per minute.

The resultant hardness pattern of the track shoe is given in theRockwell C scale in Fig. 9. The phantom line on the interior of thetrack shoe in Fig. 9 illustrates the depth of the hardness pattern andthe degree of hardness. It is apparent that the depth is substantiallyuniform. The hardness of the outer surface of the article is 59 to 61 onthe Rockwell C scale. This hardness decreases slowly toward the innerpart of the martensite layer. An abrupt change of hardness occurs at theinner port-ion of the hard martensite layer, and the interior of thearticle is relatively soft. The resultant article is substantially freeof distortion.

I claim:

1. A quenching apparatus for directing fluid to a heated metallicarticle, which apparatus comprises a manifold with an opening ofsuificient size to receive the article, means for supplying into saidmanifold a quench fluid which is of the same kind throughout, orificemeans communicating with said manifold for directing a substantiallycontinuous cavitation free sheet of said fluid at an acute angle againstthe entire perimeter surface of a cross section of the article, meansfor controlling the heat abstraction properties of zones of fluid insaid sheet substantially, independently of the heat abstractionproperties of adjacent zones, and means for providing relative movementbetween said metallic article andsaid manifold whereby said sheet offluid passes progressively over the entire surface of said article.

2. An apparatus for directing quench liquid to a heated article ofirregular cross section while the article is in motion at acontrolledspeed which comprises a manifold with an opening through which thearticle may pass, means for supplying into said manifold a quench liquidwhich is of the same kind throughout, an elongated orifice for directinga substantially continuous sheet of said liquid against the perimetersurface of a cross section of the article, separated chambers within themanifold communicating with said orifice, and means for directing saidliquid at difl'erent pressures to said chambers to produce a sheet ofliquid through the orifice with zones of diflerent delivery volume.

3. An apparatus for directing quench liquid to a heated article ofirregular cross section while the article is in motion at a controlledspeed which comprises a manifold with an opening through which thearticle may pass, means for supplying into said manifold a quench liquidwhich is of the same kind throughout, an elongated orifice for directinga substantially continuous sheet of said liquid against the perimetersurface of a cross sectionof the article, separated chambers within themanifold communicating with said orifice, and means for directing saidliquid at different temperatures to said chambers to produce a sheet ofliquid through the orifice with zones of different delivery temperature.

4. The method of controlling the hardness pattern developed in a heatedmetallic article upon quenching thereof which comprises subjecting saidarticle to a substantially continuous sheet of the same quench fluidthroughout such sheet and which has coexisting zones of said fluid withdiiferent heat abstraction properties that are substantially independentof the heat abstraction properties of said fluid within adjacent zonesin said sheet; and efliecting relative movement between said article andsaid sheet of quench fluid.

5. The method of controlling the hardness pattern developed in a heatedmetallic article upon quenching thereof which comprises subjecting saidarticle to a substantially continuous sheet of the same quench fluidthroughout said sheet and which has coexisting zones with differentcontrolled quantities of said fluid in said sheet, the quantity of saidfluid within a zone being substantially constant throughout each zone,and being independent of the quantity of fluid within an adjacent zonein said sheet; and effecting relative movement between said article andsaid sheet of quench fluid.

6. The method of controlling the hardness pattern developed in a heatedmetallic article upon quenching thereof which comprises subjecting saidarticle to a substantially continuous sheet of the same quench fluidthroughout said sheet and which has coexisting zones of said fluid withdiflerent controlled temperatures in said sheet, the temperature of saidfluid within a zone being substantially constant throughout the zone andbeing independent of the temperature of fluid within an adjacent zone insaid sheet, and eifecting relative movement between said article andsaid sheet of quench fluid.

7. The method of controlling the hardness pattern developed uponquenching a uniformly heated, elongated metallic article having parallelcross sections of similar shape, which comprises subjecting thesubstantially entire perimeter of such a parallel cross section in saidarticle to a continuous sheet of the same quench fluid throughout saidsheetand which has coexisting zones of said fluid with different heatabstraction properties, said zones of fluid in the sheet being blendedat their adjacent edges to prevent cavitation; and effecting relativemovement between said article and said sheet of quench fluid so thatsaid sheet advances over substantially the entire surface of saidmetallic article hardening successive perimeters of said similar crosssections.

8. The method of obtaining a substantially uniform hardness pattern uponquenching a heated metallic article having parallel, congruent,non-circular cross sections whereby different quantities of heat arecontained in the section of the article adjacent different perimeterportions of such cross sections, which comprises providing a continuoussheet of the same quench fluid throughout said sheet and which hascoexisting zones with different heat abstraction properties forcontacting substantially the entire perimeter of such a cross section,adjusting the heat abstraction properties of the zones of said quenchfluid to correspond proportionally to the quantity of heat containedadjacent said perimeter portions of such cross sections, subjecting saidmetallic article to said sheet of quench fluid while maintaining thezones of quench fluid with greatest heat abstraction properties incontact with the cross section perimeter portions that are adjacentsections of the metallic article containing the greatest quantity ofheat, and eifectin-g relative movement between said article and saidsheet of quench fluid in a direction substantially normal to saidparallel cross sections so that said sheet progressively advances oversubstantially the entire surface of said metallic article hardeningsuccessive perirneters of said cross sections of such metallic article.

9. The method of uniformly hardening an elongated steel article havingirregular, parallel, congruent cross sections which comprises heatingsaid article to above its temperature of transformation; providing asubstantially continuous sheet of quench water that is substantiallywithout cavitation and which has coexisting zones with differentquantities of said water in said zones, adjusting the quantity of saidwater in said zones to correspond proportionally to the quantity of heatcontained in said steel article adjacent perimeter portions of suchirregular cross sections, subjecting said steel article to said sheet ofwater while maintaining the zones of quench water with the greatestquantities of water in contact with the perimeter portions of said crosssections that are adjacent the greatest quantities of heat in saidarticle, and effecting relative movement between said article and saidsheet of quench water so that said sheet advances progressively oversubstantially the entire surface of said steel article.

10. In the quenching of a uniformly heated metallic article ofirregular, parallel, congruent cross sections by passing over thesurface of said article a continuous sheet of the same quench fluidthroughout said sheet and having coexisting zones of said fluid withcontrollable heat abstraction properties, the method of correctingdistortion of said article produced upon quenching which comprisesincreasing the proportional heat abstraction properties of zones offluidl contacting portions of said article in which concave distortionwas initially produced, and decreasing the proportional heat abstractionproperties of zones of fluid. contacting portions of said article inwhich convex distortion was initially produced.

11. A quenching apparatus for directing quenching fluid to a heatedmetallic article, which apparatus comprises a manifold with an openingof sufiicient size to receive the article, means for supplying into saidmanifold a quench fluid which is of the same kind throughout, orificemeans communicating with said manifold for directing a substantiallycontinuous cavitation free sheet of said fluid, means providingdifferent quantities of said fluid in distinct zones of said sheet andproviding a sub stantially uniform quantity of fluid throughout each ofsaid zones, and means for providing relative movement between saidmetallic article and said manifold whereby said sheet of fluid passesprogressively over the entire surface of said article.

References Cited in the file of this patent UNITED STATES PATENTS 12Denneen et 21. Dec. 16, 1941 Somes Sept. 8, 1942. Somes Mar. 2, 1943Somes Mar. 12, 1946 Arnoldy Oct. '14, 1947 Riegel et al. Sept. 4, 1951Secor Nov. 4, 1952 Linney June 22, 1954 Lyon Dec. 6, 1955 FOREIGNPATENTS Switzerland Feb. 16, 1939 Great Britain Mar. 15, 1949

4. THE METHOD OF CONTROLLING THE HARDNESS PATTERN DEVELOPED IN A HEATEDMETALLIC ARTICLE UPON QUENCHING THEREOF WHICH COMPRISES SUBJECTING SAIDARTICLE TO A SUBSTANTIALLY CONTINUOUS SHEET OF THE SAME QUENCH FLUIDTHROUGHOUT SUCH SHEET AND WHICH HAS COEXISTING ZONES OF SAID FLUID WITHDIFFERENT HEAT ABSTRACTION PROPERTIES THAT ARE SUBSTANTIALLY INDEPENDENTOF THE HEAT ABSTRACTION PROPERTIES OF SAID FLUID WITHIN ADJACENT ZONESIN SAID SHEET; AND EFFECTING RELATIVE MOVEMENT BETWEEN SAID ARTICLE ANDSAID SHEET OF QUENCH FLUID.